The present application claims priority under 35 U.S.C. xc2xa7119 based upon Swiss Application No. 2000 1309/00, filed on Jul. 3, 2000.
The present invention concerns a pick-up tool for the mounting of semiconductor chips onto a substrate. More particularly, the present invention relates to such pick-up tools known under the technical terms xe2x80x9cdie colletxe2x80x9d or xe2x80x9cdie bonding toolxe2x80x9d.
With the mounting of semiconductor chips, the semiconductor chips sawn out of a wafer and stuck to a foil are grasped by a pick-up tool and placed onto a substrate. Such a pick-up tool basically consists of a metal shaft and a suction device secured to it which has a cavity directed towards the component to be grasped to which vacuum can be applied via a drill hole. As soon as the suction device rests on the component, the vacuum effects the adhesion of the component to the suction device.
The attachment of the semiconductor chips to the substrate takes place with differing adhesive materials depending on the area of application. Apart from soft solder, with which the semiconductor chip is soldered to the substrate, and adhesive tape, mainly electrically conducting, silver incorporating as well as non-conducting liquid adhesives with an epoxy base are used. Recently however, adhesives have become known which are based on new molecular systems which harden in relatively shorter times. On the one hand, the adhesive layer must guarantee the adhesion of the semiconductor chip to the substrate, on the other hand it must be capable of compensating the shearing stresses which are caused for example by temperature fluctuations. Because the characteristics of the named adhesives are greatly dependent on the layer thickness, a constant adhesive layer thickness within tight limits is required in order to be able to produce reliable products with identical characteristics.
Also, in order to avoid the slightest damage to the semiconductor chips during mounting, pick-up tools are used whose suction device consists of rubber. Rubber has the additional advantage that it effectively seals the hollow chamber so that the semiconductor chip can be detached from the foil with a relatively large suction force.
These rubber tools however have the serious disadvantage that they cannot be manufactured with sufficient precision. The rubber tools are generally 2 to 3 mm thick. Expensive injection tools are necessary for manufacture. Nevertheless, the finished rubber tools have thickness deviations of 50 xcexcm and more. As a result, problems occur especially with the mounting of relatively large semiconductor chips, i.e., semiconductor chips with an edge length of 20 mm and more because the adhesive is badly distributed underneath the semiconductor chip, contains air bubbles, does not flow everywhere as far as the edges of the semiconductor chips, has irregular thickness, etc.
The object of the invention is to develop a pick-up tool which enables the perfect mounting of large semiconductor chips.
Solving of the task is achieved in accordance with an embodiment of the invention in that the pick-up tool has a suction plate made out of dimensionally stable material the surface of which facing towards the semiconductor chip has structures made of a curable adhesive. An adhesive proven and accepted in the semiconductor industry serves as the adhesive. The suction plate guarantees the rigidity or dimensional stability of the pick-up tool. The structures made of cured adhesive guarantee the necessary elasticity so that the semiconductor chip is not scratched and so that the cavity formed between the pick-up tool and the semiconductor chip is vacuum sealed.
In the following, an embodiment of the invention is explained in more detail based on the drawing.